USE OF THE MTT ASSAY FOR ESTIMATING TOXICITY IN PRIMARY ASTROCYTE ANDC6 GLIOMA CELL-CULTURES

Primary cultures of rat cortical astrocytes were exposed to 25 neuroto xic and non-neurotoxic compounds for 24 hr over a concentration range of 0.001 to 1000 mu g/ml and the effects were quantified using the MTT assay. EC(50) values were obtained for nine of the compounds in the t ested range, while increases in MTT conversion were seen at sub-cytoto xic concentrations for 12 compounds. The concentrations causing activa tion of this system were found, with some exceptions (notably organoti n compounds) to be similar to those previously reported to cause incre ases in expression of the astrocyte marker glial fibrillary acidic pro tein. MTT conversion was also measured in the C6 cell line and, with s ome exceptions, the response to toxicants was found to be the same as that in the primary cultures of astrocytes. However, this was only the case when the C6 cells were pretreated for 48 hr with 0.5 mM dibutyry l cyclic AMP. This study represents the first direct comparison betwee n primary astrocytes and C6 cells using a broad range of chemical neur otoxicants.